The invention relates to a soot filter for the exhaust from a diesel engine.
Such soot filters comprise a substantially cylindrical filter, particularly a filter made of ceramic material, which is penetrated by channels in the longitudinal direction. The walls of the channels are porous, so that exhaust gas flowing into a channel enters into neighboring channels via the pores. The ends facing against the flow direction are sealed in these neighboring channels, whereas the ends that face into the flow direction are sealed in the former channels. By this, the exhaust gas is forced to flow from a central channel into neighboring channels by way of the perforations. Soot particles therefore settle in the channels.
To regenerate the filter, at least one glow plug is provided, which has an approximately bolt-shaped glow rod, the free end of which is disposed near the filter or touches it. In conventional plugs, the free end of the glow rod is disposed relatively near the front face of the filter body, so that a local heating of the filter body can occur, thereby heating the soot particles to their ignition temperature. In order to make possible a more reliable ignition and thus a self-cleaning of the filter body, a very small distance and a relatively large contact surface between the glow plug and the filter body are required. In conventional soot filters, this is not sufficiently ensured. Due to the in part very high component and production tolerances and also due to the different coefficients of thermal expansion of the glow plug and the filter body, the precise and reliable arrangement of the glow plug at the face side of the filter body is problematic.
The object of the present invention is to provide a soot filter for diesel exhaust which overcomes the above-noted deficiencies and disadvantages of the prior art devices and methods of this general kind, and which is further improved in this respect.
With the above and other objects in view there is provided, in accordance with the invention, a soot filter for the exhaust gas of a diesel engine, comprising:
a filter body having a face;
at least one glow plug for thermally regenerating the filter body, the at least one glow plug having a glow plug shaft, a glow rod adjacent the glow plug shaft, and a contact part spring-mounted and axially displaceable on the glow rod, the contact part having a face side, averted from the glow plug shaft, pressed onto the face of the filter body.
In accordance with an added feature of the invention, the glow rod has a free end and the contact part projects beyond the free end of the glow rod.
In accordance with an additional feature of the invention, the face of the filter body is formed with a recess and the glow rod has a free end projecting into the recess.
In accordance with another feature of the invention, the contact part is braced at the glow plug shaft in a springing fashion. Preferably, there is provided a spiral spring spring-mounting the contact part.
In accordance with again an added feature of the invention, the spiral spring contacts the glow rod at least at a spring part facing the glow plug shaft.
In another advantageous embodiment, the spiral spring has a face-side winding mounted in a groove surrounding the glow plug shaft.
In accordance with again an additional feature of the invention, the contact part is a sleeve.
In accordance with again another feature of the invention, the spiral spring has an opposite face-side winding mounted in a groove surrounding the contact part. The contact part may be open at its free end or it may be sealed at its free end. Also, the free end may have a round face.
In accordance with yet an added feature of the invention, the contact part comprises an inner sleeve glidingly and displaceably mounted at the glow rod, and an outer sleeve surrounding the inner sleeve at a distance, and the sleeves are connected to each other at a face side thereof averted from the glow plug by a bearing ring formed with a plurality of through-openings. In a preferred embodiment, the contact part is a one-piece molded part.
In accordance with yet another feature of the invention, the contact part is a one-piece contact part wound from a spring wire, and the contact part is wound, at least at the free end, so as to make gliding contact with the glow rod.
In accordance with yet a further feature of the invention, the spring wire is wound in the region of the free end with windings touching each other.
In accordance with a concomitant feature of the invention, the spring wire has a substantially rectangular cross-section, or a square cross-section.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a soot filter for Diesel exhaust, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.